Issue #9516: avoid errors in sysconfig when MACOSX_DEPLOYMENT_TARGET is set in shell.

Without this patch python will fail to start properly when the environment
variable MACOSX_DEPLOYMENT_TARGET is set on MacOSX and has a value that is
not compatible with the value during Python's build. This is caused by code
in sysconfig that was only meant to be used in disutils.

sysconfig.py

@@ -389,7 +389,7 @@ def _init_posix():
         cur_target = os.getenv('MACOSX_DEPLOYMENT_TARGET', '')
         if cur_target == '':
             cur_target = cfg_target
-            os.putenv('MACOSX_DEPLOYMENT_TARGET', cfg_target)
+            os.environ['MACOSX_DEPLOYMENT_TARGET'] = cfg_target
         elif map(int, cfg_target.split('.')) > map(int, cur_target.split('.')):
             my_msg = ('$MACOSX_DEPLOYMENT_TARGET mismatch: now "%s" but "%s" during configure'
                 % (cur_target, cfg_target))

tests/test_build_ext.py

@@ -3,12 +3,13 @@ import os
 import tempfile
 import shutil
 from StringIO import StringIO
+import textwrap
 
 from distutils.core import Extension, Distribution
 from distutils.command.build_ext import build_ext
 from distutils import sysconfig
 from distutils.tests import support
-from distutils.errors import DistutilsSetupError
+from distutils.errors import DistutilsSetupError, CompileError
 
 import unittest
 from test import test_support
@@ -430,6 +431,59 @@ class BuildExtTestCase(support.TempdirManager,
         wanted = os.path.join(cmd.build_lib, 'UpdateManager', 'fdsend' + ext)
         self.assertEqual(ext_path, wanted)
 
+    @unittest.skipUnless(sys.platform == 'darwin', 'test only relevant for MacOSX')
+    def test_deployment_target(self):
+        self._try_compile_deployment_target()
+
+        orig_environ = os.environ
+        os.environ = orig_environ.copy()
+        self.addCleanup(setattr, os, 'environ', orig_environ)
+
+        os.environ['MACOSX_DEPLOYMENT_TARGET']='10.1'
+        self._try_compile_deployment_target()
+
+
+    def _try_compile_deployment_target(self):
+        deptarget_c = os.path.join(self.tmp_dir, 'deptargetmodule.c')
+
+        with open(deptarget_c, 'w') as fp:
+            fp.write(textwrap.dedent('''\
+                #include <AvailabilityMacros.h>
+
+                int dummy;
+
+                #if TARGET != MAC_OS_X_VERSION_MIN_REQUIRED
+                #error "Unexpected target"
+               #endif
+
+            '''))
+
+        target = sysconfig.get_config_var('MACOSX_DEPLOYMENT_TARGET')
+        target = tuple(map(int, target.split('.')))
+        target = '%02d%01d0' % target
+
+        deptarget_ext = Extension(
+            'deptarget',
+            [deptarget_c],
+            extra_compile_args=['-DTARGET=%s'%(target,)],
+        )
+        dist = Distribution({
+            'name': 'deptarget',
+            'ext_modules': [deptarget_ext]
+        })
+        dist.package_dir = self.tmp_dir
+        cmd = build_ext(dist)
+        cmd.build_lib = self.tmp_dir
+        cmd.build_temp = self.tmp_dir
+
+        try:
+            old_stdout = sys.stdout
+            cmd.ensure_finalized()
+            cmd.run()
+
+        except CompileError:
+            self.fail("Wrong deployment target during compilation")
+
 def test_suite():
     return unittest.makeSuite(BuildExtTestCase)
 

util.py

@@ -97,9 +97,7 @@ def get_platform ():
         from distutils.sysconfig import get_config_vars
         cfgvars = get_config_vars()
 
-        macver = os.environ.get('MACOSX_DEPLOYMENT_TARGET')
-        if not macver:
-            macver = cfgvars.get('MACOSX_DEPLOYMENT_TARGET')
+        macver = cfgvars.get('MACOSX_DEPLOYMENT_TARGET')
 
         if 1:
             # Always calculate the release of the running machine,